1. Field of the Art
This invention relates to an endoscope for use in medical examinations, and more particularly to an endoscopic image pickup assembly with an objective lens drive mechanism to move by remote control a plural number of lens groups of an optical objective lens system, to be incorporated into an observation window on a rigid tip end section at the distal of an elongated insertion instrument of an endoscope, for example, for the purpose of adjustmenting at least focal depth, image magnification rate or view field angle.
2. Prior Art
Generally, endoscopes which are in use for medical purposes are largely constituted by a manipulating head assembly to be gripped and manually operated by a hand of an operator, an elongated insertion instrument extended on the front side of the manipulating head assembly for insertion into a body cavity of a patient, and a universal cable which is led out from the manipulating head assembly and disconnectibly connected to a light source. For its functions, the elongated insertion instrument of an endoscope is successively constituted by, from its fore distal end, a rigid tip end section, an angle section and a flexible body portion. The flexible body portion occupies the major length of the elongated insertion instrument from a proximal end portion which is connected to the manipulating head assembly, and arranged to be bendable in arbitrary directions along a path of insertion. The rigid tip end section contains an illumination window or windows, an image pickup means, and an opening of a biopsy channel through which forceps or other instrument is introduced into a body cavity. The angle section is can be angularly bent by remote control from the manipulating head assembly, for turning the rigid tip end section into an arbitrary direction.
As mentioned above, the rigid tip end section contains at least an illumination window and an image pickup means. Located within the illumination window is a light emitting end of a light guide which is constituted by a bundle of fiber optics. The light guide is extended as far as the above-mentioned universal cable via the manipulating head assembly and disconnectibly connected to a light source. On the other hand, as the image pickup means, an optical objective lens system is fitted in an observation window on the rigid tip end section. In the case of an electronic endoscope, a solid-state image sensor device is located at the focus of the optical objective lens system. In the case of an optical endoscope, an image pickup end of a light guide, which is constituted by a bundle of fiber optics, is located at the focus of the optical objective lens system. A signal cable which is connected from the solid-state image sensor device or the image guide is passed through the insertion instrument along with the light guide and extended to the manipulating head assembly. An electronic endoscope which appears in the following description can be read and taken as an optical endoscope if a solid-state image sensor device and a signal cable is replaced by an image guide.
In addition to the above-mentioned component parts, an exit opening of a biopsy channel is provided on the rigid tip end section. Connected to the exit opening is a biopsy channel which is constituted by a flexible tube. Further, a wash nozzle is provided on the rigid tip end section to wash clean the observation window when contaminated. An air/water feed tube is connected to the wash nozzle. These biopsy channel and air/water feed tube are extended as far as the manipulating head assembly through the elongated insertion instrument of the endoscope.
As described above, an elongated insertion instrument of an endoscope is normally required to accommodate bundles of fiber optics, signal cable, biopsy channel and a number of feed tubes. In order to bend the angle section as described above, a pair of upper and lower operating wires or two pairs of vertical and horizontal operating wires are also passed through the insertion instrument. The fore ends of these operating wires are fixed either to the rigid tip end section or to a structural member in the proximity of the rigid tip end section. Within the angle section, the positions of the operating wires are restricted in circumferential direction. Further, the respective operating wires are extended as far as the manipulating head assembly through the flexible section of the endoscopic insertion instrument.
The optical objective lens system of the image pickup, which is normally constituted by a plural number of lenses, should preferably be capable of adjustments in focal depth, image magnification and view field angle, depending upon the position of an intracavitary portion to be examined or upon the purpose of examination. In this regard, it has been known to make part of the lenses of the optical objective lens system movable in the direction of optical axis for adjustments of focal depth, image magnification or view field angle.
As for drive means for moving a movable lens in the direction of optical axis of the objective lens system, it has been the general practice to use a control cable for shifting the position of a movable lens or lenses by remote control. In such a case, the fore end of a control cables is connected to the movable lens, while the proximal end of the cable is extended into the manipulating head assembly in such a way that an operator can shift the position of a movable lens in the direction of optical axis by remote control from the head assembly. More particularly, a control cable of this sort is usually composed of a flexible sleeve and a number of transmission members which are fitted in the flexible tube.
In this regard, in order to add to the optical objective lens system a function of varying a magnification rate, for example, it is the general practice to move, in the direction of optical axis, a movable lens assembly consisting of one or a plural number of lens groups. In the case of an optical objective lens system which permits higher image magnifications, however, difficulties are encountered in strictly positioning respective lens components and failures in this regard invariably result in unclear unfocused images. Therefore, it becomes necessary to make adjustments to remove not only machining errors which might have occurred in the machining stages of lens frames, support members and other components of an image pickup device, but also assembling errors which might have occurred in an assembling stage of the image pickup assembly. For this purpose, after assembling together an optical objective lens system and an image sensor means of an endoscopic observation unit, fine adjustments of lens positions are usually required with regard to at least part of lens components which are employed in the endoscopic observation unit.
An endoscopic observation unit including an image pickup assembly requires fine adjustments of lens positions of an optical objective lens system in a stage subsequent to its assembling stage as disclosed, for example, in Japanese Laid-Open Patent Application H11-47074. In the case of this endoscopic observation unit, a cover lens which is designed to function as a first lens of the objective lens system is located at a fore distal end of an insertion instrument, and a movable lens tube which carries a plural number of movable lenses is located behind the cover lens and movably supported on an objective lens frame. The objective lens frame is pulled back and forth to vary the distance between the movable lenses and a solid-state image sensor device. In order to adjust the focus on the image sensor after assembling the optical system into the endoscopic observation unit, the movable lens tube is moved in the direction of the optical axis toward or away from the objective lens frame. For this purpose, a lens adjustment hole is bored through the objective lens frame, and the lens tube is moved by an adjustor rod which is inserted into the adjustment hole. Further, upon completion of adjustment into an in-focus position, the lens tube is fixedly clamped to the objective lens frame by tightening set screws against the objective lens frame.
In this connection, as generally known in the art, the observation unit to be fitted into an insertion instrument of an endoscope is extremely small in size, particularly in diameter and thickness of the optical objective lens system, with movable lenses fitted in a lens tube which is extremely short in length in the direction of the optical axis. Accordingly, it suffices for the movable lens tube, which is mounted on an objective lens frame or other support member, to be moved over an extremely small distance in the direction of the optical axis. This means that fine adjustment of the distance between the movable lens tube and an image sensor device is very difficult and requires meticulous skills. In addition, due to a difficulty of securing a sufficient length of fitting engagement of the movable lens tube with the support member, misalignment or deviation of the optical axis is very likely to occur when the lens tube is fastened to an adjusted position by the use of setting screws. Further, in a case where a movable lense tube is arranged to slide on and along a lens frame, there is still another problem that abraded particles or dust occurring in sliding portions of the lens tube can deposit on lens surfaces.
In view of the difficulties as mentioned above, it is an object of the present invention to provide an endoscopic image pickup assembly which is arranged to facilitate fine adjustments of the position an optical objective lens system after assembling same into the image pickup assembly and which can fix the optical objective lens system precisely in a correct position after fine adjustments.
In accordance with the present invention, for achieving the above-stated objective, there is provided an endoscopic image pickup to be incorporated into a rigid tip end section of an endoscopic insertion instrument, the image pickup comprising: a support member; an optical assembly mounted on the support member, and composed of an objective lens system having at least a fixed lens and a movable lens adapted to move toward and away from the fixed lens in the direction of optical axis and a drive means for the movable lens; an image sensor means having a solid-state image sensor device to be located at the focus of the objective lens system; a guide means connected to the image sensor means to guide the support member of the optical assembly in the direction of optical axis of the objective lens system; and an optical assembly fixation means for fixing the support member to the guide means after sliding the support member along the guide means to bring the objective lens system into an in-focus position with respect to the image sensor device.
The optical objective lens system includes at least a fixed lens and a movable lens, each consisting of one or a plural number of lens elements. The movable lens can be constituted either by one movable lens group (consisting of one or a plural number of lens elements) or by two movable lens groups which are movable independently of each other. In the case of an objective lens system with two movable lens groups, the drive means can be constituted by a cam member which is connected to lens frames of the two movable lens groups, and a rotational drive member which is coupled with the cam member. The support member is constituted by a housing which permits movements of the two lens groups. A fixed lens frame is fixedly retained on the housing, which is provided with an optical system holder portion adapted to guide sliding movements of the movable lens frames along the inner periphery of the housing, along with a cam mount portion adapted to encase the cam member. In one particular form, the above-mentioned guide means is constituted, for example, by a slide guide which is provided with an arcuate guide surface for slidably accommodating the optical system holder portion of the housing, and an outlet opening for passing at least part of the cam mount portion of the housing to the outside. An entrance opening is provided at one end of the slide guide for installation of the optical system holder portion. The optical assembly fixation means may be set screws or an adhesive which is filled in gap spaces between the outlet opening of the slide guide and the housing to fix the optical assembly in position. In case the image sensor means is provided with a prism for turning a light path from the optical objective lens system through 90 degrees, one end of the slide guide, the end away from the above-mentioned outlet opening, can be fixedly bonded to the prism by the use of an adhesive or the like.
The above and other objects, features and advantages of the present invention will become apparent from the following particular description of the invention, taken in conjunction with the accompanying drawings which show by way of example some preferred embodiments of the invention.